We are asked to find the probability of getting a number less than 6 after rolling a die.
Recall that a fair die has 6 sides.
When you roll a die there are a total of 6 possible outcomes.
1, 2, 3, 4, 5, 6
Count how many of these outcomes are less than 6.
1, 2, 3, 4, 5
There are 5 possible outcomes of interest.
So, the probability is
There is a 5/6 probability of getting a number less than 6.